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Like humans, bats use both sides of brain to listen: study

WASHINGTON, April 28 — Just like humans, bats also use the left and right sides of their brains to process different aspects of sounds, a U.S. study suggested Monday.

Aside from humans, no other animals, not even monkeys or apes, have been found to use such brain specialization for sound processing — meaning that the left brain is better at processing fast sounds, and the right processing slow ones.

"These findings upset the notion that only humans use different sides of their brains to distinguish different aspects of sound," senior author Stuart Washington of the Georgetown University said in a statement.

Washington said the findings of asymmetrical sound processing in both human and bat brains make evolutionary sense.

"The slower timing of the right hemisphere may allow us to identify who is speaking, to gauge their emotional state via tone- of-voice and to tease out pitch in music, which is thought to be important for getting groups of people to coordinate their activities and can ultimately lead to the formation of cultures," Washington said.

Therefore, it is reasonable to understand why humans needed to evolve this asymmetry in their brains.

For mustached bats, the need is even more compelling, he said.

"Bats need to use the fast timing of the left hemisphere to distinguish communication sounds from each other, because their communication sounds have rapid changes in frequency. Otherwise, they cannot communicate with other bats, and bats are even more social than humans," said Washington.

"The bats also need to use the slow timing of the right hemisphere to use sonar — which relies on detecting small changes in frequency — to track the velocity of the fast-moving insects they fly after and eat."

This asymmetric sampling in bats is sex-dependent. Males were found to have more asymmetry than females, which is also consistent with humans.

"Women tend to use both the left and right hemispheres for language, but men largely use just the left hemisphere," Washington said.

By studying bat brains, the researchers said they may have a better understanding of certain human language disorders such as aphasia.

The study was published in the journal Frontiers of Neuroscience. (PNA/Xinhua)


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